In general, in order to reduce a vibration of a base rock and to improve an excavating speed, after first excavating a pilot tunnel using a tunnel boring machine (TBM), a tunneling work is performed with a construction method of enlargement blasting a periphery of the pilot tunnel.
According to such an excavating work, while first excavating a pilot tunnel using the TBM, a rail and a cable are installed at the bottom or a side wall of the excavated pilot tunnel. The rail is installed as a delivery means of a muck car for carrying out, for example mucks, and the cable includes, for example, a high-voltage cable for supplying power of the TBM, a water supply pipe for supplying water, and an air supply pipe for supplying air.
When together or separately performing excavation and enlargement blasting of the pilot tunnel, the rail and the cable are maintained or removed, and at the inside of the pilot tunnel, for enlargement blasting, a charge hole for injecting gunpowder into a base rock is drilled in a longitudinal direction or a transverse direction. As a tool for drilling the charge hole, a drill is used, and a leg drill or a jumbo drill is used according to a spot situation. The enlargement blasting using gunpowder is performed in a form of gradually enlarging from the inside to the outside.
When the enlargement blasting is complete, blasted mucks are put in a dump truck or a muck car and are carried out. Here, because the blasted mucks are stacked on the bottom of the pilot tunnel, the blasted mucks are put on the muck car using an equipment, for example a loader or a backhoe.
According to a TBM excavation and enlargement blasting method, i.e., enlargement blasting method simultaneously during TBM excavation of performing with a rail or a cable maintained, there is a problem that mucks may damage the rail and the cable while being stacked on the bottom of a pilot tunnel. In order to solve such a problem, by disposing the specially designed muck car on the rail at a tunnel face at which enlargement blasting is performed, mucks to be dropped to the ground may be put to the muck car, and in this case, when enlargement blasting is performed, the muck car directly receives an impact and may be damaged and a small muck may be jammed between the pilot tunnel and the muck car and thus it may be difficult to move the muck car.
Further, after the enlargement blasting is performed, until mucks stacked on the ground completely are removed, there is a problem that excavation of a pilot tunnel using the TBM is stopped. That is, while mucks are stacked on the ground by enlargement blasting, because the mucks completely block a passage, an excavation work of the pilot tunnel and a work of drilling a transverse charge hole are stopped.